The present invention relates to an improved apparatus for safely igniting a pyrotechnic device such as a flare which is suspended by a parachute following deployment from an air craft. More specifically, the present invention relates to alternative embodiments of a multiple stage ignition train mechanism for use with parachute suspended illumination flares, one embodiment with an in-line firing pin and the other with an out-of-line firing pin which moves in-line for firing, and a physical safety mechanism which blocks movement of the firing pin until the parachute is deployed.
Pyrotechnic devices such as flares produce brilliant light or intense heat without an explosion. Some flares are used for illumination purposes, for example to provide light on a battle field to better identify potential targets or during a search and rescue mission to assist in locating the objective. Parachute suspended flares provide maximum illumination time over a large area. Many of these illumination flares are deployed from air craft, for example standard U.S. Air Force illumination flares LUU-2 and LUU-19. The LUU-2 emits visible light while the LUU-19 emits infrared light only and is used with night vision goggles. These particular flares are designed to burn approximately five minutes. At an altitude of 1000 feet, the LUU-2 illuminates a circle on the ground of about 500 meters. The flare includes a timer which deploys the parachute and ignites the main candle.
Because illumination flares are designed to emit a large amount of light or energy for a significant length of time, they are often large and heavy. For example, the LUU-2 and LUU-19 are 36 inches long with a 4¾ inch outer diameter and weigh approximately 35 pounds each. It is critical that the flare ignite at the appropriate time—at a pre-set time after ejection from the aircraft—and not before. Accidental ignition prior to ejection or during loading and handling have serious repercussions including damage to equipment and personnel in the ignition area.
It is an objective of the present invention to provide a two-stage ignition train mechanism including a safety mechanism and an ignition mechanism, said safety mechanism incorporating a physical barrier prohibiting forward movement of the firing pin toward the primer and firing mechanism until the parachute is deployed. The ignition mechanism utilizes forces from parachute deployment to initiate the ignition sequence. There is no pre-load on the firing mechanism with the in-line design. It is another objective of the present invention to provide a two stage ignition train mechanism having an ignition mechanism which in a second embodiment is initially out-of-line of the firing axis and is rotated to an in-line position during the descent of the flare housing. The in-line firing pin design creates a more reliable, robust, controllable and consistent ignition sequence, however, by providing a mechanism which brings the initially out-of line firing mechanism in-line during the descent of the flare, added safety to those handling and equipment carrying the flare is achieved. With the inventive out-of-line firing mechanism, there is no pre-load on the firing mechanism. The inventive out-of-line design incorporates the use of shear pins to prevent rotation of the firing mechanism until the predetermined activation force is applied to the mechanism to shear the pin that holds the firing pin housing in place. Further, the end of the lanyard assembly is held in place to block forward motion of the firing pin until a second shear pin is sheared by a predetermined force, sufficient to cock the firing pin and bring the firing mechanism in-line with the primer compartment hole is reached. This is achieved safely with the post-launch rotation to the in-line firing position, achieving a “delayed” alignment with the firing pin and primer to the pellet cavity through the added physical barrier of the safety mechanism. Another objective of the present invention is to design a two stage ignition train system which, when dropped from forty feet, will not trigger the ignition sequence by inertia or incidental deployment of the timer or ignition train assembly.